1. Field of the Invention
The present invention pertains to an image forming apparatus and a terminal device such as a personal computer that are connected to a network, and to an image forming system that incorporates them both.
2. Description of the Related Art
In recent years, various types of office machines have increasingly come to be connected to networks and used in concert with each other. In particular, when a printer is connected to a network comprising multiple personal computers, a printer setup having superior cost performance can be established due to the fact that multiple users can jointly use the same printer.
In this type of printer setup, first, the print request and a sequence of print data are sent from the terminal device to the printer via the network. The printer receives these signals, stores the print data temporarily in an image memory, and then performs printing based on the print data (a printing operation based on a single print request such as described here will be referred to hereinafter as a ‘print job’).
Normally, a relatively inexpensive volatile memory is used for the image memory, and consequently, where the power to the printer goes out due to a sudden failure or some other reason, all of the received print job data is lost, and the print jobs cannot be performed.
As a result, up to now it has been necessary for the user to resend the print job data from the terminal device. However, for some users it is extremely inconvenient to resend the data. In addition, where the printer is located far away from the personal computer, the user often does not even know that the power to the printer has failed, and finds out for the first time that his own print job has been lost only after waiting for a period of time and then going to where the printer is located to retrieve it.
In order to eliminate these problems, a technology has been disclosed in Japanese Laid-Open Patent Application Hei 4-47750, for example, in which the received print job data is backed up in a non-volatile memory in the printer, wherein even if the power fails, the performance of the print job can be continued as soon as power is restored.
However, when using the backup method described above, a large-capacity non-volatile memory is necessary in the printer to store all of the received print job data, which increases the cost of the printer significantly.